Pd,Hg-Rich Gold and Compounds of the Au-Pd-Hg System at the Itchayvayam Mafic-Ultramafic Complex (Kamchatka, Russia) and Other Localities

Abstract

The unique minerals of the Au-Pd-Hg system in gold grains from heavy concentrates of the Itchayvayam placers and watercourses draining and ore samples of the Barany outcrop at the Itchayvayam mafic–ultramafic complex (Kamchatka, Russia) were investigated. Gold grains from watercourses draining and heavy concentrates of the Itchayvayam placers contain substitution structures formed by Pd,Hg-rich low-fineness gold (Au0.59–0.52Pd0.24–0.25Hg0.17–0.23, 580‰–660‰) and Pd,Hg-poor high-fineness gold (Au0.94–0.90Pd0.02–0.04Hg0.03, 910‰–960‰). Potarite (PdHg) without and with impurities (Au < 7.9, Cu < 3.5, Ag < 1.2 wt.%), Ag-poor high-fineness gold (Au0.91Ag0.09, 950‰), Ag,Pd,Hg-bearing middle-fineness gold (Au0.75Ag0.08Pd0.09Hg0.08—Au0.88Ag0.09Pd0.02Hg0.01, 820‰–930‰), and Pd,Hg-rich low-fineness gold with minor contents Ag and Cd (Au0.51–0.55Pd0.25–0.22Hg0.21–0.16Ag0.03–0.06Cd0.01, fineness 580‰–630‰) were observed as individual microinclusions in the ore samples of the Barany outcrop. XRD and EBSD study results show that the Pd,Hg-rich low-fineness gold is isotypic to gold and has the same structure type, but different cell dimensions. According to data obtained for the Itchayvayam and some deposits and ore occurrences with Pd,Hg-bearing gold, the stable ternary phases and solid solutions of the following compositions in the Au-Pd-Hg system have been identified: Pd,Hg-poor gold (Au0.94–0.90Pd0.02–0.04Hg0.03), Pd,Hg-rich gold (Au0.59–0.52Pd0.24–0.25Hg0.17–0.23), Au-potarite (PdHg0.62Au0.38—Pd1.04Hg0.96—Au0.80Pd0.68Hg0.52), and Au,Hg-bearing palladium (Pd0.7Au0.3Hg0.1). The genesis of Pd,Hg-rich gold is insufficiently studied. We supposed that the meteoric waters or low-temperature hydrotherms rich in Pd and Hg could lead to the replacement Pd,Hg-poor gold by Pd,Hg-rich gold. High concentrations of Pd in Pd,Hg-bearing gold indicate a genetic relationship with mafic–ultramafic rocks.

Palladian Gold: Chemical Composition, Minerals in Association, and Physicochemical Conditions of Formation at Different Types of Gold Deposits

“…Since that time, much data on new deposits with palladian gold have been published ( [11], and cited references). New data on the compositions of palladian gold and its minerals in the association have been recently obtained by the authors of this paper for such deposits as Chudnoe [29], Volkovskoe [30], Ozernoe [31] (Urals, Russia), and Bleida Far West (Morocco) [32], and for the placers and ore occurrences of the mafic-ultramafic Itchayvayam massif (Kamchatka, Russia) [33], which differ from other deposits. In this paper, we present a review of the composition of palladian gold of the systems Au-Pd, Au-Pd-Ag, Au-Pd-Hg, and Au-Pd-Cu and the more complex systems Au-Pd-Ag-Cu, Au-Pd-Ag-Hg, Au-Pd-Ag-Cu-Hg, etc.…”

“…According to dating assessments, the processes of formation of Au-Pd mineralization took place in the Archean, Proterozoic, Paleozoic, Mesozoic, and Cenozoic. [33,42]; 2. Ebeko volcano [43]; 3.…”

“…Ag-bearing palladian gold and other phases of Au-Ag-Pd system (in at.%) at the various deposits and ore occurrences: 1. Itchayvayam [33]; Norilsk deposits-2. Norilsk-1, 3.…”

“…We studied individual gold grains from the heavy concentrates of the Itchayvayam placers and watercourses draining and ore samples from the Barany outcrop of the Itchayvayam mafic-ultramafic complex (Kamchatka) [33]. Gold grains contain substitution structures formed by Pd,Hg-rich low-fineness gold (Au 0.59-0.52 Pd 0.24-0.25 Hg 0.17-0.23 , 580‰-660‰) and high-fineness gold with minor contents of Pd and Hg (Au 0.94-0.90 Pd 0.02-0.04 Hg 0.03 , 910‰-960‰) (Figure 6).…”

Editorial for the Special Issue “Native Gold as a Specific Indicator Mineral for Gold Deposits”

“…Palyanova et al [10] studied the composition and structure of uncommon Pd,Hgrich placer gold from watercourses draining the Itchayvayam mafic-ultramafic complex, Kamchatka, Russia. Their paper contains a review and a considerable amount of data on the composition of minerals in the Au-Pd-Hg system and the formation conditions of the Pd,Hg-bearing gold and Au-bearing potarite in other regions across the world.…”